Field of the Invention
This disclosure relates to an X-ray generation tube applicable to an imaging apparatus for medical diagnosis and non-destructive X-ray radiographing in a field of industrial apparatus. This disclosure specifically relates to a transmitting-type target applied to the X-ray generation tube.
Description of the Related Art
In an X-ray generation apparatus, enhancement of durability and improvement of maintenance reduction are required.
As one of main causes which determine the durability of the X-ray generation apparatus, heat-resistant properties of a target, which corresponds to an X-ray source is exemplified.
In the X-ray generation apparatus configured to irradiate a target with an electron beam and thereby generate X-ray radiation, an “X-ray generation efficiency” of the target is lower than 1%. Therefore, most of energy applied to the target is converted into heat. When “dissipation” of heat generated in the target is not sufficient, loss of adhesiveness of the target is caused by melting, evaporation, and thermal stress of the target itself, so that the heat-resistant property of the target is limited.
As a technique for improving the “X-ray generation efficiency” from the target, employing a transmitting-type target composed of a target layer of a thin-film form containing a heavy metal and a base material configured to transmit an X-ray and support the target layer is publicly known. Japanese Patent Application Publication No. JP 2009-545840 (also published as WO 2008060671) discloses a rotating anode transmitting-type target in which the “X-ray generation efficiency” is increased to 1.5 times or higher with respect to a rotating anode reflective target of the related art.
As a method of accelerating “heat dissipation” from the target to the outside, application of diamond as a base material configured to support a target layer of a laminated target is publicly known. U.S. Pat. No. 6,850,598 discloses enhancing heat dissipation properties and achieving a fine focal point by employing monocrystal diamond or polycrystalline diamond as a substrate configured to support a target layer formed of tungsten. Diamond has high heat-resistant property and high heat conductivity, and has high X-ray transmissivity, and hence is a preferable material as a base material for supporting the transmitting-type target.